GB2180299A - Pulsejet - Google Patents

Abstract

A pulsejet comprises, an intake 1, a tailpipe 4 and a reverse flow duct 5. Hot gases produced by combustion in the combustion chamber 2 will be ejected partly from the tailpipe 4 and the remaining gases will pass through the reverse flow duct 5 sweeping with them some of the incoming air. These features will negate the requirement for mechanical valves and are stated to improve thrust, specific fuel consumption, speed limit, and altitude range and to reduce the jet noise. <IMAGE>

Description

SPECIFICATION A new design of pulsejets for aeronautical applications and land moving vehicles This invention relates to pulsejet engines. The inlet duct of the conventional pulsejet has a series of inlet valves that are spring loaded into the open position. When the pressure rises into the chamber the valves are forced to close and the expanding gases are then ejected through the jet pipe and propelling nozzle, thus the depression created allows the valves to open and repeat the cycle.

The major difficulty is the insufficient life of the vibrating valves which must be very light and quick acting but have great resistance to vibration fatigue. The other main drawbacks is its 400-500 mph operating speed limit and limited altitude range due to the increase in specific fuel consumption, hence it is unsuitable as an aircraft engine. It also has a loud and vibratory noise.

According to the present invention the spring-loaded valves are dispensed with and the intake is so shaped to allow the air to enter freely from the intake and a tailpipe and a reverse flow duct. During expansion the hot gases will be ejected partly from the tailpipe and the remaining gases will pass through a reverse flow duct. The latter part of the hot gases will sweep with it some of the incoming air thus increasing the thrust and reducing the jet noise.

Therefore, the intake duct will not be completely closed during the expansion process as it happens in the conventional design, hence reducing the engine form drag and consequently increasing the net thrust.

The relative importance of the air flow which reenters from the tail pipe will be less than that in the conventional design, hence its effect on the pressure within the engine and the resulting engine thrust and specific fuel consumption. This will increase the operating speed limit and the altitude range. The smooth transfer from low to high pressures within the combustion chamber is expected to reduce the noise. These improvements on the conventional design makes the new design a possible candidate for aircraft applications. The inherent features of the new design especially dispensing with the spring loaded valves and the reduced pulsating noise makes it convenient for land moving vehicles.

A specified embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows the initial suction process Figure 2 shows the ignition process Figure 3 shows the expansion and exhaust process Figure 4 shows the recycle suction process Referring to the drawing, air is drawn through the carefully designed intake 1 into the combustion chamber 2. This air is mixed with the injected fuel, and burned when the fuel-air mixture becomes ignitable using the spark plug 3 as shown in Fig. 2.

The resulting pressure rise forces part of the combustion gases to expand and be ejected rearwards through the tail-pipe 4. The other part will expand through the reverse flow duct 5 sweeping with it some of the fresh incoming air. This will increase the resulting thrust and reduce the jet noise.

A depression will be created by exhausting the gases thus allowing a new fresh charge of air to be drawn in through the carefully designed intake, tailpipe and the reverse flow duct. At this stage the engine is ready to begin another cycle.

1. A new design of pulsejets for aeronautical applications and land moving vehicles in which the spring loaded valves are dispensed with and the intake is so shaped to allow the air to enter freely from the intake and tailpipe and a reverse flow duct. Hence reducing the relative importance of the air entering from the tailpipe, thus improving the thrust and specific fuel consumption and increasing the speed limit and altitude range. This new design keeps the intake duct open without being completely closed during the expansion process. Hence reduces the engine-form drag and boosts the net thrust.

Since part of the hot gases will be ejected from the reverse flow duct, some of the incoming air will be swept with it, thus reducing the average exit temperature and consequently the jet noise.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (1)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   SPECIFICATION A new design of pulsejets for aeronautical applications and land moving vehicles This invention relates to pulsejet engines. The inlet duct of the conventional pulsejet has a series of inlet valves that are spring loaded into the open position. When the pressure rises into the chamber the valves are forced to close and the expanding gases are then ejected through the jet pipe and propelling nozzle, thus the depression created allows the valves to open and repeat the cycle.

   The major difficulty is the insufficient life of the vibrating valves which must be very light and quick acting but have great resistance to vibration fatigue. The other main drawbacks is its 400-500 mph operating speed limit and limited altitude range due to the increase in specific fuel consumption, hence it is unsuitable as an aircraft engine. It also has a loud and vibratory noise.

   According to the present invention the spring-loaded valves are dispensed with and the intake is so shaped to allow the air to enter freely from the intake and a tailpipe and a reverse flow duct. During expansion the hot gases will be ejected partly from the tailpipe and the remaining gases will pass through a reverse flow duct. The latter part of the hot gases will sweep with it some of the incoming air thus increasing the thrust and reducing the jet noise.

   Therefore, the intake duct will not be completely closed during the expansion process as it happens in the conventional design, hence reducing the engine form drag and consequently increasing the net thrust.

   The relative importance of the air flow which reenters from the tail pipe will be less than that in the conventional design, hence its effect on the pressure within the engine and the resulting engine thrust and specific fuel consumption. This will increase the operating speed limit and the altitude range. The smooth transfer from low to high pressures within the combustion chamber is expected to reduce the noise. These improvements on the conventional design makes the new design a possible candidate for aircraft applications. The inherent features of the new design especially dispensing with the spring loaded valves and the reduced pulsating noise makes it convenient for land moving vehicles.

   A specified embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which: Figure 1 shows the initial suction process Figure 2 shows the ignition process Figure 3 shows the expansion and exhaust process Figure 4 shows the recycle suction process Referring to the drawing, air is drawn through the carefully designed intake 1 into the combustion chamber 2. This air is mixed with the injected fuel, and burned when the fuel-air mixture becomes ignitable using the spark plug 3 as shown in Fig. 2.

   The resulting pressure rise forces part of the combustion gases to expand and be ejected rearwards through the tail-pipe 4. The other part will expand through the reverse flow duct 5 sweeping with it some of the fresh incoming air. This will increase the resulting thrust and reduce the jet noise.

   A depression will be created by exhausting the gases thus allowing a new fresh charge of air to be drawn in through the carefully designed intake, tailpipe and the reverse flow duct. At this stage the engine is ready to begin another cycle.

   1. A new design of pulsejets for aeronautical applications and land moving vehicles in which the spring loaded valves are dispensed with and the intake is so shaped to allow the air to enter freely from the intake and tailpipe and a reverse flow duct. Hence reducing the relative importance of the air entering from the tailpipe, thus improving the thrust and specific fuel consumption and increasing the speed limit and altitude range. This new design keeps the intake duct open without being completely closed during the expansion process. Hence reduces the engine-form drag and boosts the net thrust.

   Since part of the hot gases will be ejected from the reverse flow duct, some of the incoming air will be swept with it, thus reducing the average exit temperature and consequently the jet noise.